Energy conservation is of great interest in the consumer electronics field, and in particular, in the field of home appliances. One of the best ways to conserve energy in home appliances is to reduce the ON-time of an appliance. One such appliance that is capable of a reduction in ON-time is a clothes dryer. The ON-time of a dryer can be directly correlated to the amount of water remaining in clothes being dried in the dryer. Washing machines, whether for home use or commercial use, include a spin cycle to extract water from the clothes being washed, prior to drying, thus reducing dryer ON-time, and increasing overall power conservation in home or commercial appliances
To reduce dryer ON-time, consumers are requesting increased rotational speeds in today's washing machines due to the desire for less dryer ON-time. Faster spin rates can be used to wring more water out of clothing, making the drying process more efficient. One of the biggest problems however, with increasing the spin speed in a washer to promote further water extraction is the need for better imbalance detection and improved vibration control. If clothes undergoing the spin cycle are not balanced within the tub of the washer, an imbalance will occur and result in loud noises such as knocking when the inner tub hits the outer walls, increased vibration of the tub and overall machine body, and other detrimental conditions. In most instances, the spin cycle is stopped due to the imbalance and full water extraction is not achieved, resulting in an in increase in dryer ON-time.
Currently, a load imbalance during a washer spin cycle is most commonly detected using a mechanical switch that detects when the washer drum is displaced beyond a threshold value. Displacement of the tub results in activation of the switch and the machine is typically turned off. Other types of imbalance detection devices rely on shock sensors or motor characteristics to denote when an imbalance exists, such as monitoring the torque of the motor or monitoring currents and voltages to sense changes in the power being used. A sudden increase in torque or use in power means that an imbalance has occurred during the spin cycle. These types of devices are adequate to detect imbalances at slower speeds, but not at today's higher appliance speeds. Many times, a load that is well balanced at a low speed or at the commencement of the spin cycle, can become imbalanced at increased speeds. In addition, known load imbalance detection devices are only capable of detecting an imbalance after it has occurred and provides no prediction of an upcoming imbalance situation or countermeasures.
Accordingly, there is a need for a system and method for predicting rotational imbalance in a high speed device prior to the imbalance occurring. In addition, there is a need for a device that provides countermeasures to correct the imbalance after it is detected. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.